Speaker
Description
Factorization is one of the central organizing principles in Quantum Chromodynamics (QCD) and, more broadly, in all of physics. It allows us to separate dynamics occurring at different energy, length, or time scales — turning complex problems into manageable ones and enabling precise predictions at collider experiments such as the LHC.
At the core of this framework lies the factorization of collinear singularities, which leads to the universality of parton distribution functions (PDFs). This universality is what allows us to describe a wide range of high-energy processes with the same non-perturbative input,
providing the essential bridge between theory and experiment in QCD.
In this talk, I will focus on how and why factorization can break down when two partons become collinear, particularly in space-like configurations relevant to hadron–hadron collisions. Using explicit one- and two-loop results, I will show how color correlations among
non-collinear partons lead to subtle violations of collinear factorization, and how these effects challenge the strict universality on which modern QCD predictions are built.
The discussion will also address the physical implications of these violations — such as the appearance of “super-leading” logarithms in hadronic cross sections — and the delicate mechanisms through which QCD may restore factorization at the observable level.